perf(arrow): build repeated constant string/binary columns without per-row clones - #3080
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perf(arrow): build repeated constant string/binary columns without per-row clones#3080anoopj wants to merge 1 commit into
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…r-row clones create_primitive_array_repeated built a throwaway `vec![value.clone(); num_rows]` for the Utf8/Binary/LargeBinary/FixedSizeBinary arms before handing it to the array constructor. For strings that clones the value into num_rows separate heap allocations per batch; the binary arms allocate a throwaway intermediate Vec. Stream the single value straight into the Arrow buffer via `from_iter_values` with `std::iter::repeat_n` instead. Benchmarks (release, throwaway harness, old vs new toggled on this file only): - leaf create_primitive_array_repeated (Utf8, 8192-row batch): 23.0 -> 4.1 ns/row (5.6x) - full scan select(x, _partition) over a real manifest + 262k-row parquet file, string-partitioned: 20.9 -> 5.7 ns/row (3.7x) Note that the gain is allocation-counts and scales with how much of the projection is the string partition column. Fixes apache#3079
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Which issue does this PR close?
Fixes #3079
What changes are included in this PR?
create_primitive_array_repeatedbuilt a throwawayvec![value.clone(); num_rows]for the Utf8/Binary/LargeBinary/FixedSizeBinary arms before handing it to the array constructor. For strings that clones the value into num_rows separate heap allocations per batch; the binary arms allocate a throwaway intermediate Vec.Stream the single value straight into the Arrow buffer via
from_iter_valueswithstd::iter::repeat_ninstead.Benchmarks (release, throwaway harness, old vs new toggled on this file only):
Note that the gain is allocation-counts and scales with how much of the projection is the string partition column.
Are these changes tested?
New + old tests